1. Field of the Invention
The invention relates to a fastening unit having a blind rivet nut, a washer and a screw with a screw head and a threaded shank. The blind rivet nut has a set head and a rivet shank and the washer is held on the blind rivet nut by the screw.
2. Discussion of Background Information
Fastening units of this type have proven useful, e.g., for fastening functions in which a threaded connection is necessary in thin-walled materials, such as, e.g., metal sheets, into which a thread cannot normally be cut. The fastening unit is thereby fastened in a metal sheet in the manner of a blind rivet. The term metal sheet is used below to represent all thin-walled elements to which, for example, a component is to be fastened.
A fastening unit is known from DE 101 267 47 C2, in which the placement of the fastening unit and the fastening of a component on a metal sheet takes place in one operation. The fastening unit is inserted through the component to be fastened and, at the same time, through an opening of the metal sheet to which the component is to be fastened. The set head is subsequently shaped by rotating the screw of the fastening unit, so that a firm connection is produced. The torque that is introduced into the blind rivet nut of the fastening unit by threading in the screw is transferred to the metal sheet, the opening in the metal sheet being embodied or formed in a polygonal manner and the blind rivet nut has a corresponding cross section for this purpose.
It is often problematic to bring the polygonal cross section of the blind rivet nut into line with the polygonal opening in the metal sheet, above all when the blind rivet nut has already been guided through the component to be fastened. The fastening unit is generally first guided through the component and through the metal sheet, the screw of the fastening unit being tightened in a subsequent operation with the aid of a placing tool.